1. Field
Embodiments of the present invention generally relate to a data sending and receiving terminal and, in particular, to a data sending and receiving terminal which is connected to external information terminals through a wired/wireless interface and sends and receives data by using multi-input multi-output technology.
2. Discussion of the Related Art
Mobile communication technology is evolving to the 4th generation mobile communications. A core technology of the 4th generation mobile communication technology is multi-input multi-output (MIMO) technology. MIMO technology utilizes a multiple antenna signal processing scheme which sends and receives data by using multiple antennas in a mobile environment.
By sending and receiving data simultaneously through a plurality of antennas, MIMO technology implements broadband wireless data communication and significantly enhances data sending and receiving speed, thereby increasing data transfer rate. Based on MIMO technology, if signals are transmitted through N antennas arranged in the sending side along with N antennas arranged in the receiver side, an N times increase in transfer rate can be obtained.
In particular, if MIMO technology is used together with OFDM (Orthogonal Frequency Division Multiplexing), which has been incorporated into LTE (Long Term Evolution) technology representing the 4th generation mobile communication technology, high speed data transmission and high data capacity can be obtained, by which a communication environment optimized for multimedia services can be realized. OFDM technology, which employs a scheme that assigns data into multiple frequency and time ranges, can divide a single channel into several sub-channels; by allowing overlap between the sub-channels, bandwidth is saved and frequency interference can be minimized as the frequency band is divided into hundreds of sub-bands.
Demand for small sized (or smaller-sized) devices for sending and receiving data is rapidly growing, where the device is attached to an information terminal, such as a computer or a mobile phone, and relays data between the information terminal and a mobile communication network or between the information terminal and a wireless Internet network. However, MIMO technology requires multiple antennas and cannot be easily applied to a small sized device for sending and receiving data because of a coupling problem among the antennas and limited dimensions (or capacity) for installing multiple antennas.
Recently, a new LTE frequency band lower than the pre-existing 700 MHz frequency band of 3GPP bands 12, 13, and 17 has been assigned. Accordingly, the ground plane of an antenna, namely, the size of a printed circuit board (PCB), should be enlarged. Due to the limited dimensions of a small sized terminal, however, it is not easy to design an antenna ground plane appropriate for the new LTE frequency band.